#include<cstdio>
#include<algorithm>
int v[805],i,n,j,p,k,ct=0;;
using namespace std;
int cautbin(int val)
{
    int start=0;int step(1<<20);
    for(;step;step>>=1)
    {
        int index=start+step;
        if (index>n) continue;
        if(v[index]<=val) start=index;
    }return start;
}
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++) scanf("%d",&v[i]);
    sort(v+1,v+n+1);
    for(i=1;i<=n-2;i++)
    for(j=i+1;i<=n-1;i++)
    {
        k=v[i]+v[j];
        p=cautbin(k-1)+1;
        ct=ct+n-p;

    }
}